Recently, optical fiber apparatuses adopting light emitting diodes (LEDs) as light sources have gradually held considerable market share. The luminescence efficiency of the LEDs is about 5% to 8%, and the LEDs have different luminescence spectrums available for selection, including red, green and blue spectrums. The LEDs have excellent luminescence spectrums, i.e. having a high spectrum peak value and a narrow spectrum width, and, therefore, can be used as light sources for optical fiber apparatuses.
However, the dilemma encountered in most optical fiber apparatuses is that the cross-sectional area of the light beam emitted by a LED often being much greater than the light incident surface of an optical fiber. Under the condition of Etendue conservation and the limitation in diameter of an optical fiber, the light beam within the tolerable divergence angle may be effectively coupled to the optical fiber. Therefore, limited by the tolerable divergence angle of an optical fiber, conventional light sources fail to effectively achieve the satisfied light-extraction efficiency and optical-coupling efficiency.